(Spoilers for anyone not caught up to fifth episode of the season)
I'm gonna be blunt: I have very low hopes that we're going to get a light ending.
Anything else that ended this year wasn't as dark as Supernatural, except Game of Thrones, which had a better ending than it could have (though it still could have been better).
Look how the season's going already. Rowena went to hell doing a Heroic Sacrifice (Vegeta much?), and Kevin can't go to heaven. Heaven's on the verge of collapse due to lack of angels (unless Jack making more angels made a difference?), which will mean Kevin soon won't be the only ghost wandering Earth. Dean drove Castiel away, and Sam and Dean's final opponent is the all-powerful God himself, who not only created evey universe but manipulated the events the whole time, except with Amara. Furthermore he clearly represents the writers themselves (parallelled by the books), who delight in torturing Sam and Dean to the point some people think it's a fetish. Even God at least wanted them to keep winning before now.
Sam and Dean's strongest allies are gone. Jack, Gabriel, and Death are dead, there's Billie but she doesn't like to intervene, Cosmic Entity seems evil, and Amara left Earth, showing she's not going to take Dean's side any more than God's, even though she's probably the only one that can actually kill him. We also know Michael's getting out, but he'll be insane, and I doubt he'll want to take Sam and Dean's side either, he masterminded the angels' whole plan to let Lucifer destroy the world and then recreate it.
I suspected earlier that God was actually testing Sam and Dean one last time and if they passed the test he'd make them his successors or something, and they'd change the whole world for the better. But from Atomic Monsters, we're clear his intent is to kill Sam and Dean and end the world, and he can revive anyone he wants except archangels. Lilith was first, he'll probably also revive Azazel to screw with Sam and Dean. There's a good chance that, to further stack the odds, he'll revive Alastair, Asmodeus, Abaddon, Dagon, and Ramiel.
Also Lilith's pretty much gonna get away with eating babies, there's a 1% chance she'll ever be re-killed (or even reappear after last episode), especially with any and all weapons that can kill Princes of Hell or white-eyed demons destroyed. Unless Sam drinks demon blood, but even then Lilith wanted him to kill her, she has no reason to die again.
What do you think? Will we get an ending as dark as the rest of the series or will it end on a good note?